Direct-view storage tube having controlled write-through

ABSTRACT

A flood gun control grid is placed between an electron gun and a backing electrode, and covers a given portion of the area of the backing electrode. This control grid is connected to control potentials sufficient to cutoff flood gun electrons. Write-gun electrons, having sufficiently high velocity, will not be cutoff by the flood control grid and will penetrate the grid and backing electrode to write directly on the portion of the viewing screen of the tube which is blocked by the flood-control grid.

United States Patent Inventor Joseph Burns Pequannock, NJ.

Appl. No. 843,495

Filed July 22, 1969 Patented Feb. 23, 1971 Assignee Fairchild Camera and Instrument Corporation Mountain View, Calif.

DIRECT-VIEW STORAGE TUBE HAVING CONTROLLED WRITE-THROUGH 9 Claims, 3 Drawing Figs.

U.S. (I 313/68, 315/12 Int. Cl. H0lj 31/52, H0lj31/58,l-l0lj31/62 Field ofSearch 3 13/68 (A), 68

(Pl/drP/IOK .mezz/pi I 'mwcr/ui flflW/VGj-ZI i I I (ffl/FiSZfO/PMFIJQ- 22.; I 43' 1 flsflz/r/ aflt rwapfjzz-w f I 25 1. Z7 42 j 2- [56] References Cited UNITED STATES PATENTS 3,086,139 4/1963 Lehrer 315/12 3,214,631 10/1965 Anderson. 315/12 3,249,784 5/1966 Burns 1 313/68 3,281,601 10/1966 Sheftelmam. 250/203 FOREIGN PATENTS 783,719 9/1957 Great Britain Primary Examiner-Robert Sega] Attorneys-Roger S. Borovoy, Alan H. MacPherson and Charles L. Botsford PATENTED FEB23 IBYI James J.

DlllllECT-WEW STORAGE TUBE HAVING CONTRGLLED WRITE-THROUGH BRIEF SUMMARY OF INVENTION This invention relates to direct-view storage tubes, and more particularly relates to a direct-view storage tube in which portions of the viewable area can be written upon with the write gun while flood electrons cause the presentation of stored information on other portions of the viewable screen.

Direct-view storage tubes are old and well known and generally consist of a phosphor screen which is disposed behind a backing electrode mesh. The backing electrode mesh is constructed such that an electron gun, known as a write gun, can scan in any desired pattern across the backing electrode mesh to deposit thereon a particular electrostatic pattern. A flood gun, which generates low-energy electrons, uniformly distributed over the entire surface of the backing electrode, then directs electrons toward the backing electrode. These flood electrons will pass trough the backing electrode to the phosphor screen in accordance with the electrostatic pattern on the backing electrode. The image presented upon the phosphor screen will then be a relatively permanent image and will last so long as the flood electrons are present and so long as the electrostatic pattern is maintained on the backing electrode. The backing electrode can be erased or updated as desired so that new images can be written on the backing electrode which are subsequently presented on the phosphor screen. The screen may be normally illuminated and the image developed as a dark line on the illuminated screen, or the image may be developed as a bright line on a dark screen.

It is desirable in many applications to be able to write nonstored information on the face of the display screen while the electrostatic image of the backing electrode is being presented on the screen by the flood electrons. For example, it would be desirable in many applications to be able to write a cursor on the periphery of a particular type of presentation. It might also be desirable to write identifying information on a P.P.I.-type radar display identifying various targets, and being writethrough to update or vary the identifying information. Such controlled write-through cannot be accomplished in presentday tubes since any attempt to write with the high-energy write beam while an image is being presented with the flood electrons would simply cause the formation of an electrostatic pattern on the backing electrode which would be permanently presented along with the previously stored information on the backing electrode. The term permanently" herein refers to the storage of information on the backing electrode which would produce a continuous visual presentation of information under the stimulus of flood electrons, and ignores the slow discharge of the pattern due to ion discharge and electrical discharge in general. This information can, of course, be erased by removing the charge pattern of the backing electrode.

In accordance with the resent invention, a direct-view storage tube is constructed with an auxiliary control grid arrangement which permits the simultaneous presentation on given phosphor screen of both permanently stored information from the flood electrons passing through a backing electrode as well as controlled write-through information which is nonpermanently presented using, for example, the write gun of the tube. More particularly, and in accordance with the invention, a control screen having a desired shape, a desired shape, such as an annular disc or portion of a circle or the like, is disposed in a plane generally parallel to the phosphor screen and is interpose between the phosphor screen and the collector electrode. This control screen or electrode is then connected to such a potential that it will block the passage of the low-energy flood electrons through a portion of the backing electrode while permitting the passage of higher energy electrons which will penetrate the control grid and backing elec trode grid to be applied directly to the phosphor screen. Thus,

write-through on the phosphor screen can take place in the manner of any television type, temporary presentation, which relies upon the direct and continued application of primary electrons from a write gun to the phosphor screen.

For example, and in accordance with the invention, a control grid having a smaller area than the backing electrode may be positioned between the collector grid and backing electrode, or between the backing electrode and a suppressor grid, or between the suppressor grid and the phosphor screen. In a further embodiment of the invention, portions of the backing electrode per so may be coated with an electron-permeable membrane which would permit passage of high-energy writegun electrons, but cut off low-energy flood electrons. Note that this embodiment, unlike those using separate control electrodes prevent storage on control electrode-masked portions of the tube.

The invention has particular application to the presentation of cursor information around the periphery of a P.P.l.-type radar display. .This cursor information can be continually updated as by rotation of the cursor if desired. Other obvious applications of the invention would include the writing of identifying labels and the like in selected areas of a direct-view storage tube as around the periphery of the tube or at any particular area of the tube face.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal cross-sectional view through the axis of a direct-view storage tube constructed in accordance with the present invention.

FIG. 2 is a cross-sectional view taken across the section line 2-2 in FIG. 1.

FIG. 3 is a plan view of an alternative type of write-through control grid to that shown in FIGS. 1 and 2.

DETAILED DESCRIPTION OF DRAWINGS Referring first to FIGS. 1 and 2, there is illustrated therein a direct-view storage tube of a generally conventional type which, however, further includes the write-through control grid of the present invention. In FIGS. 1 and 2, the convention components include the gloss bulb 10, secured to a suitable neck member 11 to form an evacuated chamber containing the tube components. Member ii is provided with a suitable plug-in base 12 which carries a plurality of conductive pins 13 which can be connected to various circuit components in order to appropriately control the electron gun structure within the tube. The tube is then provided with a conventional write gun, schematically shown as block 14, and a conventional flood gun, schematically shown as block 15. Write gun 14 contains a cathode connected to terminal 16 which i accessible from the exterior of the tube, and is connectable to suitable cathode potentials. Similarly, the flood gun 15 is provided with an externally-available terminal 17. Write gun l4 cooperates with a suitable write-beam control structure and lens, schematically shown by the block 18, where the lens portion, for example, may be connected to an external ground. Block 18 would contain conventional magnetic or electrostatic deflection means and focusing means well known to the art.

The display portion of the tube within bulb 10 includes a conventional phosphor screen 19 disposed adjacent the circular display end of the tube. A conventional conductive coating 29 extends over the phosphor screen 19 and is connected to a high-voltage terminal 21. A suppressor mesh 22 may be provided if high contrast storage operation is desired, and is located to the right of conductive coating 20. Suppressor 22 is connected to external-available member 23.

A standard backing electrode 24 is then located to the right of suppressor 22 where the backing electrode consists of any conventional type of mesh, with a dielectric surface facing to the right in FIG. 1 and the conductive mesh facing to the left. The backing electrode 24 and its dielectric surface 240 then serve, in effect, as a large array of discrete capacitor elements which can be controllably charged by electrons from the write gun 14, thereby to impart a particular electrostatic image on the dielectric surface 24a of backing electrode 24. Backing electrode 24 is connected to terminal 25, which is external of the tube.

The tube further contains a standard collector grid 26 which is connected to the terminal 27. Collector grid 26 acts to collect the secondary electrons emitted from the backing electrode 24 during writing on the dielectric surface 240, and collects primary return electrons, and terminates the flood gun collimating electrode (not shown), and acts as an ion repeller.

It will be noted that each of the grids or meshes 22, 24 and 26 are carried within suitable mounting rings 28, 29 and 30 which are conventionally supported within the tube and with respect to one another. This support structure is not shown herein as it is not important to the present invention l general, the various control grids can have any desired conventional spacing with respect to one another and any conventional mesh configuration. By way of example, the collector grid 26 may be a 250 electrode mesh spaced from the backing electrode by from .l5 inches to .35 inches. The backing electrode may be a 500 line mesh, and may be spaced from the suppressor grid by from 0.030 to 0.10 inches. The suppressor grid, which may also be a 500 line mesh, may be spaced from the conductive coating 20 by from .2 to .35 inches.

In accordance with the present invention, a novel writethrough control grid is interposed between the phosphor screen ad the collector grid 26. Control grid 40 may consist of a conductive screen having a 100 line mesh, which is spaced about .1 inches and up to about .2 inches from the backing electrode in a inch diameter display tube arrangement. These dimensions are not critical and can be varied depending upon tube parameters and he voltages which are applied to the various elements.

The write-through control grid 40 is then connected to terminal 41, which is eternal of the tube and to which a control potential ma be connected. It will be seen that the control grid 40 is an annular grid mounted between support rings 42 and 43. The control grid 40 may have a radial dimension which is any desired dimension depending po the type display which is to be written on the portion of phosphor screen 19, which is in registry with an annular area of control grid 40.

In operation, the write gun 14 will initially, by virtu of the write beam control 18, deposit a particular electrostatic pattern on the backing electrode 24. The flood gun l5 thereafter directs low-energy electrons uniformly toward and distributed over the surface backing electrode 24, whereby the electrostatic pattern on backing electrode 24 permits the flood gun electrons to reach the phosphor screen 19 in order to excite an image of the electrostatic pattern on the backing electrode 24 on the phosphor screen 19. This, of course, is the standard operation of a typical direct-view storage tube. In this operation, the following potentials with respect to ground would be applied to the following terminals:

Terminal 21 KV Terminal 23 +25 volts (-35 volt pulses coincident with erase pulses on backing electrode) Terminal 25 Terminal 27 +200 volts Terminal 16 2 KV Terminal 17 ground (zero volts) In accordance with the present invention the flood gun electrons from the flood gun 15 can b prevented from passing through the annular region of backing electrode 24, thus preventing the forming of an electrostatic image of backing electrode 24 on the phosphor screen 19 in the annular region. This is accomplished by applying a biasing potential to writethrough control grid terminal 41, for example of l0 volts. This potential, however, which is sufficient to block passage of flood gun electrons is insufficient to block the passage of highenergy electrons from the write gun 14 (or some other write gun within the system) whereby high-energy electrons from the write gun, during the time of operation of the flood gun, can write a pattern directly on the phosphor screen 19 area in registry with write-through control grid 40. Thus, the write gun 14 can be controlled in any desired pattern on the outer, annular area of the tube while a stored image is being presented on the remainder of the tube. This permits, for example, the presentation of a movable cursor on the outer periphery of the stored image presented on the tube. To be able to. display stored information over the entire surface of screen 19, it is only necessary to bring control grid 40 t about volts FIGS. 1 and 2 describe the area in which controlled writethrough is possible as an outer, annular area for the tube. lt will be apparent hat any area shape can be selected where, for

example, one semicircular portion of the display of the tube can be used for storage presentation, while the other for a I write-through presentation. To this end, the write-through control grid 50 of FIG. 3 may be used in lace of the annular control grid 40 of FIGS. 1 and 2.

It is possible, if desired, to place control grid 40 between backing electrode 24 and suppressor 22, or between screen 19 and suppressor 22. If supressor 22 is eliminated, control grid 40 may be directly between screen 19 and backing electrode 24.

In another embodiment, the function the control grid can'be served by depositing an electron permeable coating such as an aluminum coating, over the backing electrode 24. Those areas which are coated will permit passage of high-energy write gun electrons, but will prevent passageof flood gun electrons. This can b one by lacquering the area to be coated, and thereafter coating the lacquer with about SOOangstroms thickness aluminum, and then baking out the lacquer. Note that this em bodiment cannot be controlled such that the blocked area can be selectively used to present stored information, or writethrough information.

Although there has been described a-preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. Therefore, this invention is to be limited not by the specific disclosure herein, but only by the appended claims.

I claim:

1 A direct-view storage tube having controlled writethrough portions on the display surface thereon; said directview storage tube comprising:

a. an evacuated housing having a display surface and a luminescent coating on the interior of said display surface;

b. a backing electrode mesh in the vicinity of nd substantially coextensive with said display surface and extending across at least portions of said interior of said display surface and being adapted to store an electrostatic image thereon;

c. a write electron gun means disposed within said housing for generating a beam of electrons toward said backing electrode; said backing electrode disposed between said coating and said write gun'means;

d. control means for controlling the direction of the electron beam of said write gun means;

e. a flood electron gun mans disposed within said housing for generating a flood o low-energy electrons toward said backing electrode; said backing electrode disposed between said coating and said flood electron gun means; and

f. and a write-through control grid; said write-through control grid being disposed parallel to and adjacent said backing electrode; said write-through grid being disposed between said coating and each of said write gun means and flood electron gun means; said write-through control grid extending over only a selected portion substantially less than the full surface area of said backing electrode.

2. The direct-view storage tube of claim 1 wherein said flood gun means to prevent passage of flood gun electrons through said control grid extending over said selected portion of said backing electrode and to said coating.

3. The direct-view storage tube of claim 1 wherein said control grid has an annular configuration 4. The directw'iew storage tube of claim 1 wherein said control grid has a semicircular configuration.

5. The direct-view storage tube of claim 2 which includes a collector grid disposed between said write gun means and flood gun means and said control grid; said collector grid being generally coextensive in surface area with said backing electrode.

6. The direct-view storage tube of claim 5 wherein said write-through control grid is biased with respect to said flood gun means to prevent passage of flood gun electrons through said control grid to said selected portion of said backing electrode.

7. in a direct-view storage tube of the type having, within an evacuated envelope, the serial disposition of a display screen, a backing electrode in the vicinity of and substantially coextensive with said display screen and capable of having an electrostatic image formed thereon by a movable, focused beam of electrons, and a write electron gun means and flood electron gun means for respectively illuminating said backing electrode with a focused beam of high-energy electrons and a flood of uniform low-energy electrons; the improvement which comprises: a control grid positioned between said backing electrode and said write gun means and flood gun means and in the vicinity of said backing electrode; said control grid having a configuration extending over only an area substantially smaller than that f said backing electrode; and means for biasing said control grid to a potential with respect to said flood electron gun means which prevents passage of flood electrons through said control grid, and which permits passage of relatively higher energy electrons therethrough to permit electron beamwriting on said display screen at areas thereof conforming to the configuration of said control grid.

8. The directwiew storage tube of claim 7 wherein said control grid has an annular configuration.

9. The direct-view storage tube of claim 7 wherein said control grid has a semicircular configuration. 

2. The direct-view storage tube of claim 1 wherein said flood gun means to prevent passage of flood gun electrons through said control grid extending over said selected portion of said backing electrode and to said coating.
 3. The direct-view storage tube of claim 1 wherein said control grid has an annular configuration
 4. The direct-view storage tube of claim 1 wherein said control grid has a semicircular configuration.
 5. The direct-view storage tube of claim 2 which includes a collector grid disposed between said write gun means and flood gun means and said control grid; said collector grid being generally coextensive in surface area with said backing electrode.
 6. The direct-view storage tube of claim 5 wherein said write-through control grid is biased with respect to said flood gun means to prevent passage of flood gun electrons through said control grid to said selected portion of said backing electrode.
 7. In a direct-view storage tube of the type having, within an evacuated envelope, the serial disposition of a display screen, a backing electrode in the vicinity of and substantially coextensive with said display screen and capable of having an electrostatic image formed thereon by a movable, focused beam of electrons, and a write electron gun means and flood electron gun means for respectively illuminating said backing electrode with a focused beam of high-energy electrons and a flood of uniform low-energy electrons; the improvement which comprises: a control grid positioned between said backing electrode and said write gun means and flood gun means and in the vicinity of said backing electrode; said control grid having a configuration extending over only an area substantially smaller than that f said backing electrode; and means for biasing said control grid to a potential with respect to said flood electron gun means which prevents passage of flood electrons through said control grid, and which permits passage of relatively higher energy electrons therethrough to permit electron beam writing on said display screen at areas thereof conforming to the configuration of said control grid.
 8. The direct-view storage tube of claim 7 wherein said control grid has an annular configuration.
 9. The direct-view storage tube of claim 7 wherein said control grid has a semicircular configuration. 